Fig. 17. Transverse section through the procephalic lobes of an embryo of the same age. _gr._ Section of hemicircular groove in procephalic lobe.
Fig. 18. Transverse section through the thoracic region of an embryo of the same age as fig. 8.
Fig. 19. Section through the procephalic lobes of an embryo of the same age.
Fig. 20_a_, _b_, _c_, _d_, _e_. Five sections through an embryo of the same age as fig. 9. _a_ and _b_ are sections through the procephalic lobes, _c_ through the front part of the thorax. _d_ cuts transversely the posterior parts of the thorax, and longitudinally and horizontally the ventral surface of the abdomen. _e_ cuts the posterior part of the abdomen longitudinally and horizontally, and shews the commencement of the mesenteron.
Fig. 21. Longitudinal and vertical section of an embryo of the same age. The section passes somewhat to one side of the middle line, and shews the structure of the nervous system.
Fig. 22. Transverse section through the dorsal part of the abdomen of an embryo of the same stage as fig. 9.
Fig. 1. Transverse section through the pelvic fin of an embryo of _Scyllium_ belonging to stage P[5], magnified 50 diameters. _bp._ basipterygium. _br._ fin ray. _m._ muscle. _h f._ horny fibres supporting the peripheral part of the fin.
[Footnote 5: I employ here the same letters to indicate the stages as in my "Monograph on Elasmobranch
Fig. 2. Pelvic fin of a very young female embryo of _Scyllium stellare_, magnified 16 diameters. _bp._ basipterygium. _pu._ pubic process of pelvic girdle (cut across below). _il._ iliac process of pelvic girdle. _fo._ foramen.
Fig. 3. Pelvic fin of a young male embryo of _Scyllium stellare_, magnified 16 diameters. _bp._ basipterygium. _mo._ process of basipterygium continued into clasper. _il._ iliac process of pelvic girdle. _pu._ pubic section of pelvic girdle.
Fig. 4. Transverse section through the ventral part of the trunk of an embryo _Scyllium_ of stage P, in the region of the pectoral fins, to shew how the fins are attached to the body, magnified 18 diameters. _br._ cartilaginous fin-ray. _bp._ basipterygium. _m._ muscle of fin. _mp._ muscle-plate.
Fig. 5. Transverse section through the ventral part of the trunk of an embryo _Scyllium_ of stage P, in the region of the pelvic fin, on the same scale as fig. 4. _bp._ basipterygium. _br._ cartilaginous fin-rays. _m._ muscle of the fins. _mp._ muscle-plate.